Method for jacketing fibrous ducts

ABSTRACT

A method and apparatus for applying a jacket sheet to an open ended porous fibrous duct, by wrapping the sheet around the duct, applying end closures to the ends of the duct, at least one such closure having a vacuum connection so that by reduction of pressure in the interior of the duct, the external atmospheric pressure will serve to hold the jacket sheet snugly against the duct, and interconnecting the adjacent edges of the jacket sheet while it is being held snugly against the exterior of the duct under the influence of the reduced internal pressure and the external atmospheric pressure.

United States Patent Waksman et a1.

[ 1 June 6,1972

[72] Inventors: David Waksman, Roeland Park, Kans;

James R. Stewart, Kansas City, Mo.

Certain-Teed Saint Gobain Insulation Corporation, Bala Cynwyd, Pa.

[22] Filed: Apr. 14, 1970 [21] Appl.No.: 28,369

[73] Assignee:

[52] US. Cl ..156/287, 156/47, 264/90 [51] Int. Cl. ..B29c 17/07 [58] Field of Search 156/285, 286, 287, 475, 104,

Marshack Buckbee 264/90 X Marsh, Jr.

3,040,154 6/1962 ....l56l286 X 2,941,570 6/1960 Plym 156/475 2,766,808 10/1956 Kleiber et al... .156/286 X 1,263,462 4/1918 Payne 1 56/286 1,898,043 2/1933 Foster ..264/90 X Primary Examiner-Benjamin A. Borchelt Assistant Examiner1-laro1d Tudor Attorney-Synnestvedt & Lechner [5 7] ABSTRACT A method and apparatus for applying a jacket sheet to an open ended porous fibrous duct, by wrapping the sheet around the duct, applying end closures to the ends of the duct, at least one such closure having a vacuum connection so that by reduction of pressure in the interior of the duct, the external atmospheric pressure will serve to hold the jacket sheet snugly against the duct, and interconnecting the adjacent edges of the jacket sheet while it is being held snugly against the exterior of the duct under the influence of the reduced internal pressure and the external atmospheric pressure.

6 Claims, 6 Drawing Figures PATENTEDJUH 6 i972 SHEET 1 [IF 2 fgnj.

PATENTEDJUH 51922 SHEET 2 OF 2 METHOD FOR JACKETING FIBROUS DUCTS This invention relates to the jacketing of fibrous ducts, and particularly to the application of a sheet type jacket to glass fiber ducts.

The invention has several general objectives, including the following: 3

First, the invention facilitates the jacketing operation and thereby increases the efficiency of production of jacketed ducts.

Another major objective isto provide a method and apparatus for improving the snugness of fit of a jacket upon the exterior surface of a porous fibrous duct.

It is a further object of the invention to provide for the use of jacketing material in sheet form, lengths of the sheet jacketing material being wrapped around the duct to be jacketed, with opposite edge portions positioned adjacent to each other. Moreover, the invention contemplates utilizing a vacuum system for reducing the pressure in the interior of the duct, and thereby providefor snugly holding the jacket sheet against the exterior surface of the duct during the jacket fastening or sealing operation.

Another object of the invention is to simplify the operation of sealing the adjacent edges of the jacket sheet.

The invention still further contemplates provision of equipment for the above purposes while providing adjustability so that the equipment is adaptable to the jacketing of ducts of various diameters or sizes.

How the foregoing objects and advantages are attained, together with others which will occur to those skilled in the art, will appear more fully from the following description referring to the accompanying drawings, in which:

FIG. 1 is a side elevational view of equipment according to the present invention, the equipment here being shown in use in the application of a jacket to a duct of one particular size;

FIG. 2 is an end view taken from the right of FIG. 1;

FIG. 3 is a ,view similar to FIG. 1 but illustrating the jacketing operation at a different stage than that shown in FIG. 1;

FIG. 4 is a transverse sectional view on an enlarged scale as compared with FIGS. 1 to 3, and illustrating still another stage in the'jacketing operation;

FIG. 5 is a fragmentary view on the scale of FIG. 4, illustrating certain features of the jacketed duct; and

F IG. 6 is a view similar to FIG. 2 but illustrating adjustment of the equipment to provide for the handling and jacketing of a duct of larger size than the duct appearing in FIGS. 1 to 5.

Although the invention is applicable to the jacketing of porous ducts of various types, the invention is particularly useful in connection with the jacketing of glass fiber ducts used for various purposes such as in air'conditioning, heating, and other air handling systems. Ducts of this type are commonly formed of glass fibers bonded together by a binder, for instance a synthetic resin binder. The wall of such ducts ordinarily is quite porous, so that without a impervious jacket, the duct would not well serve its purpose in air handling systems of the kind mentioned above. Moreover, the porosity of such ducts is a characteristic which is important in the carrying out of the method of the present invention.

Ducts of the general kind described above are of various sizes, ranging from about 3 to about 40 inches in outside diameter, and such ducts may have a wall thickness from about inch up to about 3 inches. In a typical duct of this sort, the wall is 1 inch in thickness and the duct has an inside diameter of 4 inches and an outside diameter of 6 inches. Pieces or sections of 72 inches length are commonly employed, although the length may of course be varied for different purposes. The invention is also applicable to ducts of various specific end configurations, such as ducts adapted for butt joints at the ends or for shiplap joints at the ends. The ducts may also be of various cross sectional shapes, although cylindrical ducts are most common.

In the illustration of FIGS. 1 to 5 inclusive, there is shown the typical duct of l-inch wall thickness, 6-inch outside diameter. While such ducts are commonly of 72 inches length, the length as illustrated in FIGS. 1 to 5 would be of the order of 36 inches.

The equipment in FIGS. 1 to'5 comprises a base or support 7 having an upright board or retaining element 8 at one end and a similar element 9 toward the other end, the element 8 in the embodiment shown being fixed and the element 9 being pivotally mounted upon the base or support 7 by means of the hinge indicated at 10, so that this element 9 may either occupy the upright position shown in full lines or the dot and dash position indicated at 9a.

In the embodiment of the apparatus illustrated, the elements 8 and 9 are adapted to serve as retaining means for closure plugs 11 and 12 which may be used if desired to aid in positioning and closing the opposite open ends of the duct indicated at D. The closure devices 11 and 12 may be formed in frustoconical shape, so that the inner ends of these devices may actually be inserted into the open ends of the duct.

A pair of adjustable platforms 13-13 are mounted upon the base by means of bolts 14. By loosening the bolts 14 and shifting the position of the platforms 13 toward or away from each other, as permitted by the slots 15 formed in the support 7, the inner edges of the platforms may be adjusted relative to each other in a manner providing a trough for receiving and positioning ducts of different sizes. While the jacketing material may be supplied from various sources, such as a roll, if desired a stack of jacket sheets of appropriate size may be mounted upon the platforms 13, as is indicated at S in the drawings. A stack of these sheets may be placed upon the platforms across the trough or channel between the inner edges of the platforms, and then the duct sections are sequentially mounted over the channel provided between the inner edges of the platforms and each such duct is wrapped with a jacket sheet S and the sheet is secured thereto iri'the manner to be explained.

- In' the sequence of operations performed in applying a jacket to a duct, with the form of equipment illustrated, after placement of the stack of jacket sheets in the position as indicated, and with the displaceable retaining board 9 swung downwardly to the position indicated at 90, one end of a duct is then placed upon the closure device 1 1. Closure device 12 isthen inserted into the other end of the duct and the displaceable board 9 is brought up to the full line position shown in FIG. 1, thereby serving to retain the duct and the closures 11 and 12 in assembled relation as illustrated. Advantageously a torsion spring is associated with the hinge 10 so that the spring normally urges the board 9 upwardly to its full line position, i.e., the position in which it serves to retain the closure plugs 11 and 12 in assembled relation with the duct. If desired, a releaseable latch may be provided for temporarily retaining the board 9 in the displaced position indicated at 9a.

Although the closure plug 12 may be mounted upon the board 9, such mounting is not necessary in the embodiment illustrated and, in fact, with a manual type of operation it is convenient to have the plug 12 separate from the board 9. At the opposite end of the duct, although the plug 11 may be arranged for separate handling, as with the plug 12, in the embodiment illustrated it is preferred that the plug 11 be mounted upon the upright retaining board 8. As one illustration of an arrangement used according to the invention, the plug 11 has a central passage therethrough in which a tube 16 is mounted, this tube projecting outwardly through an elongated slot 17 (see FIG. 2) formed in the board 8. The tube being threaded at its outer end and provided with a nut 18 so that the assembly of the tube and plug 11 may be fastened to the board 8. A flexible vacuum hose connection such as indicated at 19 is also associated with the tube 16, and with this arrangement it will be seen that a vacuum connection is provided to the interior of the duct, so that the pressure may be reduced therein.

After the duct is mounted in the manner described above and with the vacuum system in operation, one of the jacket sheets S is flexed upwardly around the duct in the manner clearly shown in FIG. 4, with the opposite edges of the sheet overlapped in the zone at the top of the duct. Since the pressure is reduced on the interior of the duct, this tends to draw air inwardly through the porous duct wall into the interior, and

this results in the external atmospheric pressure holding the jacket sheet snugly-against the exterior surface of the duct. The holding action will continue until the desired sealing operation is performed. Various different techniques may be employed for interconnecting the adjacent edge portions of the jacket sheet. One preferred technique for this purpose is to provide jacket sheets of dimensions providing a slight overlap of opposite edge portions, and then interconnect the overlapped edge portions by an adhesive means. For this purpose an adhesive tape may be employed. A bracket 20 is desirably provided toward the top of the retaining board 8 in order to mount a supply spool 21 of adhesive tape, which may readily be drawn from the spool as indicated at T in FIG. 3 and applied to the lapped joint of the jacket sheet along the top of the duct. After the adhesive tape is cut to an appropriate length,

. the seal may be completed bymeans of a hand tool carrying a pressure roller 22 (see FIG. 4) applying pressure over the tape along the joint; This hand tool may also incorporate a small warm air blower such as indicated diagrammatically at 23 in FIG. 4. The warmed air may also berelied upon for promoting the tight seal. A piece of jacketed duct prepared as just described is illustrated in FIG. 5, the jacket being partially broken away and the view also showing the adhesive tape T.

After a duct piece or section has been jacketed in the manner described above, the retaining board 9 may be displaced and the closure member 12 removed and the jacketed duct taken away replaced by another duct to be jacketed. When the plugs 11 and 12 are assembled with the duct and the vacuum system isin operation, the vacuum system itself will aid in maintaining the plugs and the duct in the desired positions. When a jacket sheet is wrapped around the duct, the pressure-tending to draw the plugs into the open ends of the duct will of course be increased, but since the wall of the duct is porous, some air may enter into the ends of the duct wall and flow through the duct wall into the interior. This is desirable in order to avoid excessive decrease in pressure within the duct such as might tend to cause the duct to collapse under the influence of the atmospheric pressure on the outside of the jacket sheet. For this same reason, it may be desirable with certain ducts to provide a jacket whose dimension lengthwise of the duct is slightly less than the length of the duct to thereby provide further leakage areas through the ends of the duct through which-air may enter-into the interior and thus avoid excessive increase in pressure within the duct.

The provision of some leakage area permitting flow of some air into the interior of the duct is also of importance in avoiding burning up or overloading of the vacuum or suction fan motor.

border to accommodate a duct of larger size as indicated at D1 in FIG. 6, the platforms 13 are preferably separated from each other and fastened in the positions indicated in full lines in FIG. 6, thereby providing a wider trough between the adjacent or inner edges of the platforms. A stack of wider jacketsheets S1 are then placed upon the platforms and the larger ducts D1 sequentially brought to jacketing position in the manner described above.

For the handling of ducts of larger size, duct closure members of larger size may be used so as to effectively close the open ends of the larger duct. One such larger sized closure member 1 1a is indicated in FIG. 6, and it will here be seen that the central tube 16 which is associated with the vacuum connection 19 is now mounted at the upper end of the slot 17 in the retaining board 8, in order to bring the center of the closure plug 11a to the proper elevation above the platforms 13, as needed in the handling of the larger sized duct. It will be understood that at the opposite end of the duct, a closure plug corresponding to plug 12 shown in FIGS. 1 and 3 will also be used with the larger duct, and will be proportioned to fit the larger'open end requiring closure. This latter plug or closure device will then be retained in its proper position in relation to the duct by means of the same displaceable or pivoted retainer board 9, as in the use of the equipment with the smaller duct as illustrated in FIGS. I to 4.

It will thus be seen that equipment of the type illustrated in the drawings is readily adaptable to the handling and jacketing of ducts of various sizes. Moreover, it should also be understood that the technique of the present invention may be achieved with modified forms of equipment, for instance the closure members 11 and 12 may be omitted and the planar surfaces of the end boards 8 and 9 may be brought directly against the end surfaces of a duct to be jacketed. The vacuum connection would of course still be made through at least one of the end boards, and even with the vacuum connection positioned at a given point, the equipment would still be readily usable with ducts of a wide range of sizes. In an arrangement in which the end boards are brought directly into contact with the end surfaces of the duct, the boards may be formed at least in part of rubber or other resilient material, for instance by'applying a sponge rubber facing to the side of each board presented toward the duct.

If desired the equipment may also be proportioned so that more than one duct may be positioned in'the equipment in end-to-end relation, thereby providing for jacketing ducts in multiple, the same vacuum system being thereby concurrently used for simultaneous jacketing of more than one duct.

It will also be understood that insofar as the method is concerned, numerous other variations in equipment may be employed. In all cases, the vacuum system described above is of advantage in that the jacket sheets are held snugly to the exterior surface of the duct pieces under the influence of atmospheric pressure. This improves the fit of the jacket and avoids subsequent loosening or shifting of the jacket during installation or use.

Since the jacket sheet is held to the exterior surface of the duct being jacketed under the influence of the vacuum drawn within the interior of the duct, the system ordinarily prevents application of more than a single jacket sheet to any given duct being jacketed. There is no tendency in this system for the jacketing operation to retain more than one sheet in contact with a duct.

It will be understood that various phases of the opera as described above may readily be automated, but whether the various steps are carried out manually or automatically, the technique of the present inventionigreatly facilitates the application of jackets and greatly improves the snugness of the jacket and also the uniformity of application, from duct to duct.

The technique of the present invention may be used with jacketing materials or jacket sheets formed in a variety of ways, but preferably, the sheet material employed comprises a multiple layer laminate, for instance a foil-scrim-kraft paper laminate. The sheet material should have, some appreciable flexibility, and in view of this, in a foil-scrim-Kraft paper laminate, these various layers would be quite thin, especially the foil layer. A typical jacket sheet of this type may have a total thickness of about 0.005 inch. A heavy aluminum foil layer of sufiicient thickness to provide the desired structural strength would have greater rigidity than preferred in accordance with the present invention. The reason for this is that the system of the invention relies upon the pressure difthe exterior surface of the duct, and the snugness of engage! ment is improved by using a sheet having substantial flexibility. l t 1 In a foil-scrim-Kraft paper jacketing sheet, the scrim may comprise threads or filaments or natural fibers or of synthetic resins. Moreover, if desired the fibrous layer in the laminate may be composed of glass fibers, for instance in the form of a loose random glass fiber mat. Still other forms of jacketing sheets may be employed, such as laminates made of aluminum foil, scrim or glass fibers and a layer of a heat sealable resin, such as polyvinyl chloride resin or vinylchloride-vinylidine copolymer resin. Moreover, a jacket may be utilized in which the laminate comprises a Kraft paper layer, a fibrous layer and a resinous layer of the kind just referred to. v

In addition to the desirable flexibility, the jacket sheet must of course possess the desired characteristic of impermeability, since the important function of the jacket is to contribute impermeability to the pervious or porous duct wall which is characteristic with ducts formed of fibrous material such as glass fibers.

The technique employed in interconnecting the edges of the jacket sheet which is wrapped around the duct will vary somewhat, depending upon the character of the sheet itself. In general, the application of an adhesive tape may be employed with virtually any appropriate jacket sheet. However, where a heat sealable layer is embodied in the jacket sheet material, the sealing may be effected by bringing the layers of heat scalable resin of the opposite edge portions of the jacket together along the line of junction and then applying pressure and heat to effect a seal, even without the use of a separate adhesive tape. In all instances, however, the vacuum system is of advantage in establishing the snug jacket fit and also in holding the jacket sheet in position during the sealing operation.

Although vacuum connections may be provided at both ends of the duct being jacketed, this is ordinarily not needed and the use of a vacuum connection at only one end, as shown in the illustrative embodiment of the drawings is of advantage from the standpoint of simplicity.

We claim:

1. A method for applying a jacket sheet to an open ended porous fibrous duct, which method comprises applying to an end of the duct a closure having a vacuum connection communicating with the interior of the duct, closing the other end of the duct to provide for pressure reduction in the interior of the duct and for air flow into the interior through the porous duct wall, wrapping a jacket sheet around the duct and holding the jacket sheet snugly against the exterior surface of the duct under the influence of atmospheric pressure with the opposite edges of the sheet adjacent each other, and while the jacket sheet is thus held snugly against the exterior surface of the duct interconnecting said adjacent edges of the jacket sheet.

2. A method as defined in claim 1 in which the adjacent edges of the jacket sheet are interconnected by applying adhesive tape thereto.

3. A method as defined in claim 1 in which the adjacent edge portions of the jacket sheet are overlapped and in which the overlapped edge portions are interconnected by applying a tape strip thereto and by adhesively interconnecting the tape strip and the edge portions.

4. A method as defined in claim 1 in which the jacket sheet incorporates heat sealable resin material and in which the adjacent edge portions of the jacket sheet are brought into contact with each other and are interconnected by heat sealing said resin material.

5. A method for applying a jacket sheet to an open ended porous fibrous duct, which method comprises wrapping a jacket sheet around the duct with opposite edges of the sheet adjacent each other, closing the ends of-the duct and evacuating the interior to draw air inwardly through the porous duct wall and thereby hold the wrapped sheet snugly against the exterior of the duct under the influence of atmospheric pressure, and while the jacket material is so held interconnecting the adjacent edge portions of the jacket sheet.

6. A method for applying a jacket sheet to an open ended porous fibrous duct, which method comprises applying to an end of the duct a closure having a vacuum connection communicating with the interior of the duct, applying a substantially imperforate closure to the other end of the duct thereby closing the interior of the duct and provide for reduction of the pressure therein, wrapping a jacket sheet around the duct with opposite edge portions adjacent each other and thereby provide for snug engagement of the jacket sheet with the exterior of the duct under the influence of atmospheric pressure, and while the jacket sheet is in such snug engagement with the duct adhesively interconnecting the adjacent edge portions of the jacket sheet. 

2. A method as defined in claim 1 in which the adjacent edges of the jacket sheet are interconnected by applying adhesive tape thereto.
 3. A method as defined in claim 1 in which the adjacent edge portions of the jacket sheet are overlapped and in which the overlapped edge portions are interconnected by applying a tape strip thereto and by adhesively interconnecting the tape strip and the edge portions.
 4. A method as defined in claim 1 in which the jacket sheet incorporates heat sealable resin material and in which the adjacent edge portions of the jacket sheet are brought into contact with each other and are interconnected by heat sealing said resin material.
 5. A method for applying a jacket sheet to an open ended porous fibrous duct, which method comprises wrapping a jacket sheet around the duct with opposite edges of the sheet adjacent each other, closing the ends of the duct and evacuating the interior to draw air inwardly through the porous duct wall and thereby hold the wrapped sheet snugly against the exterior of the duct under the influence of atmospheric pressure, and while the jacket material is so held interconnecting the adjacent edge portions of the jacket sheet.
 6. A method for applying a jacket sheet to an open ended porous fibrous duct, which method comprises applying to an end of the duct a closure having a vacuum connection communicating with the interior of the duct, applying a substantially imperforate closure to the other end of the duct thereby closing the interior of the duct and provide for reduction of the pressure therein, wrapping a jacket sheet around the duct with opposite edge portions adjacent each other and thereby provide for snug engagement of the jacket sheet with the exterior of the duct under the influence of atmospheric pressure, and while the jacket sheet is in such snug engagement with the duct adhesively interconnecting the adjacent edge portions of the jacket sheet. 